Wait until your return is processed. It will be either accepted or rejected by the IRS. If it gets accepted then you will need to complete an amendment (correction) to add your 1099 income. If your return gets rejected by the IRS, when you log back in to make the necessary corrections, you can add your 1099 BEFORE you e-file again. Please see the below on how to check you e-file status and how to process an amendment.

https://ttlc.intuit.com/replies/3319882

https://ttlc.intuit.com/replies/3288565